Mercury Outboard Maintenance Schedule (2.2 thru 40 HP)

A Mercury outboard maintenance schedule is a plan of action for carrying out a process of maintaining or preserving a boat motor based on the manufacture specifications. It’s a written plan of procedure that lists a series of things to be done to the motor at or during a particular time or period.

Performing regular maintenance to your Mercury outboard motor is critical. It’s estimated that 73 percent of engine repair work can be avoided by following the maintenance instructions in a repair manual. Moreover, an outboard motor should never be left sitting dormant for an extended period of time (six or seven months). Always refer to the service manual’s inspection and maintenance procedure section if a motor has been sitting for this long.

Only when a routine maintenance program has been implemented can the boat owner expect to attain satisfactory performance at minimal cost. Keep in mind that postponing scheduled maintenance can result in a snowball effect. In the example of a blown head gasket, which can be a relatively cheap repair job, can develop into sever engine malfunction and require complete engine overhaul to fix the motor.

Follow this inspector and maintenance guide so as to extend the life of the motor and help you avoid major overhaul and repair work.

Inspection and Maintenance Schedule


Before Each Use

  1. Ensure the lanyard stop switch is in working order and stops the engine.
  2. Visually inspect the condition of the fuel system for deterioration or leakage, repair if necessary.
  3. Ensure the outboard is fastened tightly on transom.
  4. Check Mercury outboard steering system for binding or loose components (on applicable models).
  5. Visually inspect the outboard’s steering link rod fasteners for proper tightness, refer to repair manual for more information.
  6. Check the outboard’s propeller, visually checking for damaged blades; e.g. cracks, chips or bends.

After Each Use

  1. Always flush out the Mercury outboard’s cooling system after each use if the motor was being operated in salty or polluted water.
  2. If the engine was being operated in saltwater, wash off all salt deposits with a high pressure hose. Be sure to flush out the exhaust outlet of the propeller and gearcase using clean fresh water.

Every 100 Hours of Use or Once Yearly, Whichever Occurs First

  1. Lubricate all lubrication points, refer to your Mercury outboard repair manual for a list of lubrication points. Lubricate more frequently if the motor is used in salt water.
  2. Inspect and clean spark plugs. Replace broken or worn spark plugs.
  3. Check fuel line filter for contaminants; e.g. grime, water etc.
  4. If the motor is hesitating when accelerating, bogging or experiencing poor fuel consumption, check carburetor adjustments, if required.
  5. Check corrosion control anodes. Check more frequently if the motor receives a lot of abuse or when used in salt water.
  6. Drain and replace gearcase lubricant. Ensure there is no water in the gear case when changing it.
  7. Lubricate splines on the drive shaft. Either refer to the factory service manual for how-to procedures or have a repair shop perform the work
  8. Electric start models – Inspect condition of battery; e.g. state of charge, expiration date, etc.
  9. Remote control models – Check or make control cable adjustments. Refer to repair manual for procedures.
  10. Use Power Tune Engine Cleaner to remove engine grime or deposits.
  11. Check tightness of bolts, nuts, and other fasteners. Refer to repair manual for factory torque specifications.
  12. Clean fuel tank pick up filter.

Every 300 Hours of Use or Three Years

Replace water pump impeller with new parts (more often if overheating occurs or reduced water pressure is noted).*

These items should be serviced with the help of a repair manual.

Always use a Mercury 40hp repair manual when performing maintenance to your Mercury outboard motor. More advanced maintenance procedures are listed in the manual.

2 thoughts on “Mercury Outboard Maintenance Schedule (2.2 thru 40 HP)

  • January 31, 2017 at 1:28 am

    Does this apply to my 50 horsepower mercury outboard?

    • January 31, 2017 at 1:29 am

      Most of this applies to all outboards. But you should refer to a repair manual for complete maintenance procedures. Here is a list of some of the models it will apply to:

      1989-2003 Mercury 15 HP 2-Stroke
      1989-2002 Mercury 8 HP
      1989-2003 Mercury 6 HP
      1989-2003 Mercury 9.9 HP Sailpower, XR10/MAG 10/Viking 10
      1992-2001 Mercury Sea Pro/Marathon 10
      1988-1990 15 HP Mercury
      1975-1978, 1979-1985 4.5HP Mercury
      1968-1972, 1973-1990 20 HP Mercury (Model 200)
      1968-1987 6 HP Mercury
      1969-1974 4 HP Mercury (Model 40)
      1965-1978 9.8 HP Mercury (Model 110)
      1980-1982 3.6 HP Mercury
      1979-1985 9.8HP Mercury (Model 9.8)
      1984-1989 2.2HP Mercury
      1986-1988 25HP Mercury
      1965-1995 3.9 HP Mercury (Model 39)
      1991-1999 Mercury 9.9 HP
      1976-1980 4HP Mercury
      1979-1983 40 HP Mercury (Model 40)
      1980-1984 25 HP Mercury
      1981-1983 18 HP Mercury
      1989-2002 Mercury Sea Pro/Marathon 15
      1984-1985 18HP Mercury (Model 18XD)
      1986-1987 4HP Mercury
      1971-1974 40 HP Mercury (Model 402)
      1969-1978, 1979-1985 7.5HP Mercury
      1983-1986 3.5 HP Mercury
      1990-2000 Mercury 8 HP Sailmate
      1965-1996 35HP Mercury (Model 350)
      1970-1994 40HP Mercury (Model 400)
      1984-1998 25HP Mercury (Model 25XD)
      1986-1997 9.9 HP Mercury
      1990-1991 2.2 HP (Model 3.0)
      1984-1989 35 HP Mercury (Model 35)
      2004-2005 Mercury Verado 200 225 250 275
      2008-2009 40 50 60 EFI Big Foot & Non-BigFoot 4-cylinder
      1986-1990 8HP Mercury


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